Pendulum relay controlled startstop telegraph transmitter



Dec. 30, 1947. G. c. HARTLEY ET AL PENDULUM RELAY CONTROLLED START-STOP TELEGRAPH TRANSMITTER 1 Filed March 10, 1943 s Sheets-Sheet 1 A Inventor w l v 037 L" T ,WQI T @Q A v a T A a 4 a A q q A N S m Q m m 2 \M QM & v u m T a l N Q gng mm m wo f: m; QQLQ Q22 mesa LC UL W No 8 m PM 8 G :0 8 u 8 up W6 w W.

csQc. HARTLEY ETAL 2,433,362

PENDULUM RELAY CONTROLLED START-STOP TELEGRAPH TRANSMITTER Dec. 30, 1947.

Filed March 10, 1943 5 Sheets-Sheet 3 Patented Dec. 30, 1947 "PEND ULUM RELAY CONTROLLED START- STOP TELEGRAPH TRANSMITTER George Clifford Hartley and William John Reynolds, London W. C. 2, England, assignors to Standard Telephones andCablesLimited, London, England, .a British company Application March 10, 1943, Serial No. 478,735 In Great Britain March 13,1942

.26 Claims. (Cl.178--79) "The present invention-relates to telegraph systems operating witha code such as the five-unit code, and is more -particularly concerned with "circuit arrangements for transmitting and receiving such a code, which'do not involve rotating mechanical systems.

Probably the most important application of the .five-unit code'at the'present timeis in the transmission of teleprinter signals where the well known start-stop principle is employed. The power required to operate a teleprinter is derived "from an .electricmotor coupled to arotating mechanical system, and on'account of the functions which it has to performit is necessarily .an intricate and expensive machine requiring 'a relatively large amount of maintenance. There are certain cases where a telegraph channel is required to 'conveyin'forma'tion of :a limited character in which the cost of teleprinters would not be justified, particularly where the information is not required to be recorded on paper in the usual way. A typical case of this kind is that in which an electric ,power supply authority requires a meansforrperiodically reporting the indications of wattmetcrs or other like instruments located at a distance; the necessaryinformation can .in this case be conveyed by means of a 'few characters, and might be used to operate appropriate indicators, instead .ofbeing typed out. Another example is the case where .a circuit is used for the transmission of certain standardised orders to adistant-point where they might be displayed on an indicator.

.It is evident that asystemlsuitablefor thissort of service should be economical to construct and shouldrequire the minimum ofmaintenance. The present invention .provides circuit arrangements chiefly employing :ordinary .com- .mercial telephone type relays @notrequiring -any special adjustments, and not involving any motor-driven mechanical systems. These :circuits comprise a code sender which will transmit any start-stop-character; and acode receiver which can be used to "store the characters and tense them tooperate any suitable "form of indicator-or other receiving :device. The code sender could, if desired, be used to operate the printing section of an ordinary teleprinter-over:atelegraph channel and would therefore prove an economical alternative one-way "transmitter for ordinary mes-' .sages if .a :home record can be dispensed ":with.

According to the invention there is providedsa telegraph system for start-stopcode signals comprisingea pendulum relay,..means for releasing the .relay armature .from fa locked position to .=.execute '2 free oscillations, and means for returning the armature to a locked position after .a predetermined number of swings.

According to another aspect, the invention consists in a telegraph system comprising arelay ,havinga vibrating armature, andmeans for causing the said armature to time the transmission or reception of a code combination .ofsignal ele ments, each such combination comprising astart element and a stop element.

The invention will be more clearly understood by reference to the following detailed description of embodiments and to the accompanying drawings, in which Fig, 1 shows a schematic circuit diagram .ofa code sender according to the invention;

Fig. 2 shows a diagram used to explain the operation of Fig. 1;

Fig. 3 shows a schematic circuit diagram of code receiver according to the invention; and

Fig. 4 shows a diagram used to explain the operation of Fig. 3.

In order that the invention may be clearly understood, it will be assumed that the signals to be transmitted are start-stop five-unit code signals suitable for the conventional teleprinters operating .at a speed of .50 bands. It will be evident, however, that the same circuitsare adaptable for other codes and speeds: it is quite possible, for example, that in some-0f the cases mentioned above to which the invention is specially suited, the information could be conveyed on .a code with fewer units; in other circumstances more thanfive unitsmight be preferable.

In .all machine systems usingoodes, it is essential to have somemeans of sending out signals at accurately spaced intervals. In teleprinters this .is generallydone by .means of a shaft rotating at an accurately controlled speed and carrying :a cam which operates contacts once per revolution. In the present invention, use is made of a pendulum relay having an armature *whichacan execute isochronous vibrations with small damping,

-and which is adapted to operate contacts approximately at the centre of its travel, insuch man- .ner that the intervals betweensuccessive operacute free vibrations by cutting off the energising current, and so releasing it, and by a suitable circuit it may be given suitably timed impulses to maintain it indefinitely in vibration, if desired. The preferred type of relay is that which forms the subject of the co-pending British Patent No. 549,971, granted March 11, 1943. This relay is of cheap construction, and is capable of manufacture from parts similar to those of commercial telephone relays, and does not require critical adjustments, except for the oscillation frequency, which is easy to carry out.

Figs. 1 and 3 are schematic circuit diagrams according to the invention, drawn on the detached contact principle.

In order to simplify the circuits, any connection to the battery or other constant potential source is indicated by an arrow-head pointing away from a relay, and earth connections are indicated by the conventional symbol. The positive terminal of the battery is supposed to be connected to earth, though the circuit would operate the other way just as well. Generally, spark quenching arrangements, current adjusting resistances and other like accessories not essential to the invention have been omitted, and may be supplied in any suitable manner known to those skilled in the art.

The circuits are shown with all relays in .the unoperated condition, that is, the condition which holds before the battery has been switched on. Actually certain relays are normally operated during the idle periods between the transmissions of the individual characters, and these will be pointed out in the course of the explanation of -e operation of the circuits.

In the description of the circuits, use will be made of the terms mark and space, and marking and spacing. The marking condition of a line or circuit used for start-stop signals is the condition during which the circuit is temporarily idle, though ready to transmit characters, and the spacing condition is the opposite condition. The actual state of the line or circuit, that is, whether it is connected to positive or negative battery, or whether in the case of single current operation it is open or closed (and so on) during the marking condition will depend on the arrangements which have been chosen, and is immaterial, so long as the chosen conditions are consistently maintained. The signal element which is produced by the change to the marking condition will be called a marking element or mark, and the other element is the spacing element or space. Thus the start element is always a space, and the stop element is always a mark.

When the pendulum relay armature vibrates, it makes alternate swings from side to side and is always locked, and released from, the same side. The word "swing will be used .to denote one movement of the armature; a complete vibration period therefore comprises two swings.

Although in the detailed description below various particular relay timings and the like have been specified for clearness, these are not in any sense necessary to the invention, and other timings can be arranged for other cases.

Referring to Fig. 1, there is shown a schematic circuit diagram of a code sender according to the invention. It employs a pendulum relay P,

a sending relay SR which is preferably a polar telegraph relay, and a number of ordinary commercial telephone relays.

of the code sender cir uit (Fig. 1)

The line over which the signals are to be transmitted is connected to terminal TRM, which leads directly from the armature it of the sending relay SR. Transmission of the code for any character is effected by momentarily earthing by any convenient means one of the terminals I to 39 or 32, which have been labelled with the characters they represent. These terminals could, for example, be connected to a typewriter key system provided with the necessary contacts. The timing of the signals corresponding to each separate character is determined by the pendulum relay P which operates the sending relay SR at the proper times to the marking or spacing side, according to setting of the code storing relays V, W, X, Y, Z. These relays are selectively operated by code setting relays connected to the above terminals. A train of successively operated counting relays A, B, C, D, E, F and G counts the swings of the relay P, and causes it to be locked up when the transmission of the character is completed.

Grouping of characters The characters are divided into two groups depending upon whether the last unit element of the code is a marking or a spacing element; and earthing a character terminal, for example B (No. 30), operates a relay DS giving a final marking element, while operating D (No. 26), operates relay CZ and gives a final spacing element. The characters B and D h a ve the same first four unit elements, and share a code setting relay CH. All the other characters are similarly paired except K (which has four marking elements and a space), and the letter shift, which has five marking elements. As will presently be clear, neither of these characters needs a code setting relay.

Earthing a character terminal operates in series one winding of the corresponding code setting relay CA to CO and the relay DS or CZ (according to the type of the last unit element), the circuit being obvious.

Setting the operating condition of the circuit When the battery supply is first switched on to put the circuit in the operating condition, relay H operates through the contacts HR-i, and looks through its own contacts H-l. This relay remains operated all the time that the circuit is idle. Relay H operates the slow-release relay HR by closing the contacts H-Z, which thereupon opens its contacts HRI. This relay remains permanently operated for the whole of the time the circuit is working, and does not release during the transmission of the characters. Its sole purpose is to reset the idle condition of the circuit when the batteries are first switched on. Switching on the battery also operates the pendulum relay P through its holding winding h and contacts HR--l or H-l, and holds it with the armature on the PM side. Thus, in the idle or ready to operate condition, relays H and HR are operated, and the pendulum relay P is locked with the armature on the PM side.

Setting of the code storing relays When a character terminal is earthed, for example, B, relays CH and DS operate in series. CH operates relays W and X through its contacts CH-l and CH--2 respectively, and W and 2! look themselves through contacts W-I and General account assessor x r. This will cause a spacingtelement to' be transmitted for the second and. third code units.

Earthing' of other character terminals will cause the operation ot other selections of the code stor mg relays, andaspacing element is sent tor'units' corresponding to code storing relays whichhave been operated, and marking elements for those which have not. Thus since the first four code units for K and letters are all marking elements, none of the relays V to Y have tobe operated, as the code setting relay CZ only is re-* quired for K,.to operate relay Z.

Preparing the code Marking and spacing batteries are respectively connected to terminals M and +8, and thence to the marking and spacing contact [5 and I3 of the sending relay SR. The relay has two equal main windings m and s connected to battery, as shown, so that when earth is applied to m the armature I4 is operated to the marking contact 15, and when earth is applied to s it is operated to the spacing contact [3. The bias winding b is connected through a resistance Q-l to the armature to provide a current just great enough to hold the armature on the contact on which it was last placed, when there is no current in either of the main windings.

The coding contacts V-2 to Z-2 of the code storing relays are respectively associated with the counting relays B, C, D, E and F. When the character B is to be transmitted, relays W and X are operated and connect the spacing winding 5 of relay SR to relays C and D. Since the other code storing relays are not operated, the marking winding m of relay SR is connected to relaysB, E and F. Relay A is connected to the spacing Wind ing, and relay 'G tothe marking winding irrespective of the code storing relays. They correspondrespectively to the start and stop elements,

It will be understood that if the character to be transmitted had been D, relay CZ would have been operated instead" of DS, and by closing its contacts CZ--2 would haveoperated Z to prepare a spacing element for the last code unit.

The relay SR is ultimately operated by the armature of the pendulum relay P through the contacts of the counting relays, which are closed in turn in the manner to be presently explained, and the code storing relays W and X, being operated, decide that spacing elements are to be sent for the second and third units by preparing the connection of the spacing winding s of the relay SR. It will be evident that when some other character is to be sent, the code storing relays will prepare the spacing winding of SR for operation in some other selection of units.

Transmission of the code The earthing. of a character terminal, besides setting the code storingrelays, also operates relay DS or CZ as has been explained. One of'these' relays opens the contacts DS-I or CZ"I and releases relays H and P by removing the earth connection from their windings. H'opens its contacts H-l thus rendering open the earth connection during the transmission of the character, (since relay HR remains operated owing to its slow releasing character). On removal of the earth from the character terminal, relay DS or CZ is released, so that the earth connection is prepared for the subsequent locking of relay H.

The pendulum relay P on its release executes a'number of free vibrations so that the armature makes alternate contact with PS and PM at times spaced. by equal intervals, which for.v a tele raph;

speed of: 50 bands will. be 20 milliseconds; The. sequence of operations involved in transmitting; the code will be more: clearly understood from Fig: 2, in. which; the graph it indicates the operations of the pendulum relay. referred to a hortzontal time scale. The armature is initially on: the PM side and after release at t1 by relay D53 or CZ, contact. with PMwill be broken say, 12 miniseconds later, at zero time, and contact with PS is made after a negligible interval. The pendulum then swings; regularly,v the change-over occurring substantially every 20 milliseconds as shown bythe graph a.

The operationsof the various relays are shown in Fig. 2 by horizontal lines the lengths of which indicate the time during which the contacts, areoperated. The dotted portions of these lines cover the periods during which the winding is energised but before the contacts have operated. The counting relays A to G may take about 12 milliseconds to operate, and their windings are shunted by resistances qt todelay the release for about 50. milliseconds after the operating current is cut off. Relay H is not so shunted and may release in about 10 milliseconds;

At the moment 251 some of the relays V to Z. are energised as already explained and will have 0perated before. zero time. The relay H will also have released by thistime as shown in Fig. 2.

When the relay P makes contact on the PS side at zero time, the counting relay A is energised through the contactsB-l, Dl, F-I and T-J" and. through the contacts HR-2, which are closed. The sending relay SR is at the same time operated to space, giving the start signal. When relay A closes its contacts A-| at about 12 milliseconds, it prepares relay B for operation after the next swing of relay P. As already explained, contacts Al will remain closed for about 70 mil.- liseconds, that is for 50 milliseconds after disconnection on. the next swing of relay P at 20 milliseconds, to allow B to be energised when re.- lay P makes contact on the PM side at that time. When this occurs the sending relay will also be operated to mark (for'the character B). When relay B operates at about 32. milliseconds it. prepares C, and cuts off A to prevent it from being re-operated when P swings to PS next time. Relays C, D, E, F and G then operate in turn on alternate swings of the relay P in the same manner, each preparing the next one and cutting off the previous one. Meanwhile the sending relay SR is operated on each swing to mark or space as determined by the code storing relays, (givinga space at 40 and 60 milliseconds for character B).

After the operation of F, a marking stop element is given when relay P swings to P8 at milliseconds, the sending relay being energised through. the rectifier J l whose purpose will be presently explained; ,A circuit is also completed through the rectifier J2 and a resistance Q2 to the winding d of-the pendulum relay P for areason also to be. explained later on. When the pendulum finally swings back to PM at milliseconds, it looks itself upthrough the circuit including winding h prepared by contacts G-I of relay G through contacts K-l'. Relay H is also- It will be noted thatcontacts (3-3 have been.

included between the contacts E-'l and relay-F. Reference to Figs. 1 and 2 will show that when relay P swings to PM at 140 milliseconds the relay F would be again energised because E has not released. Accordingly contacts G-3 are put in to cut off relay F at about 128 milliseconds as indicated at t2.

The locking up of relays H after the completion of the transmission of the character depends upon the circuit being closed at contacts DS| and CZ| If the earth should be left connected to the character terminal, relay DS or CZ will remain operated and the circuit will be broken. H does not lock up, but HR will ultimately release, closing contacts HR--l; and H will be re-operated as soon as the earth is removed from the character terminal, so that the circuit ultimately returns to the idle condition.

Testing arrangements For testing purposes, an extra counting relay T is provided, with a test relay K controlled by a key It. On the operation'oi this relay by closing the key, relay H is cut off at the contacts K-2 and the pendulum relay P is released. Relay HR is maintained permanently operated by contacts K3. The counting relays then operate in turn as before starting from A (HR-2 being closed), until the operation of G which instead of causing P to lock up, energises relay T, which has a resistance q shunting the winding and is otherwise similar to the other counting relays. When T operates at about 148 milliseconds it bypasses contacts Fl as indicated at t; in Fig. 2 and causes the cycle to be repeated by the reoperation of A at about 172 milliseconds, after the pendulum has swung to PS at 160 milliseconds. Relay T is cut off by the contacts A2 as shown at t; to prevent its re-operation on the next swing, and the cycle is repeated indefinitely.

These operations are shown in Fig. 2. The dotted lines in the curve a represent the continued swinging of the pendulum relay P, and a second operation of A is indicated to show how the cycle re-commences after the operation of T.

The operations of the circuit may be counted and timed by means of the contacts T-2 which earths a test terminal 3| (through the contacts K4 which are closed) for each cycle. Any suitable testing device may be connected to terminal 31.

The circuit already mentioned leading from contacts F-l through rectifier J2 to the winding cl of relay P are for the purpose of giving it an impulse near the end of each cycle. While the preferred type of pendulum relay will oscillate freely for some seconds, it is necessary to sustain its oscillations over the comparatively long period of the test. The rectifiers J land J2 are provided to prevent impulses from being applied to the pendulum relay through the winding of G and the other counting relays each time they are operated.

The contacts K5 are provided to short-circuit the contacts G2 to prevent the release of the code storing relays at the end of a cycle. This enables any desired character to be continuously repeated during the test in order 'to permit distortion or other like tests to be made.

The code setting relays CA to C0 are required if any code is identified by conditions on a single wire; as would be the case if the circuit is associated with a teleprinter keyboard. It will be obvious however that in many applications these relays can be omitted altogether and the required codes set up by operating the code storing General account of the code receiver circuit (Fig. 3)

The incoming signals are applied at terminal 6 to the receiving relay RR, which is preferably a polar relay having marking and spacing contacts RRM and RR-S. The unit signals repeated by the relay RR are inspected by a series of code storing relays VV, WW, XX, YY and ZZ each of which applies an earth to a corresponding terminal I to 5 (which may be connected as desired to a receiving apparatus or storage system of any type), when the corresponding unit signal is a space. A pendulum relay PB determines that the inspection shall be made during a short interval, say, about 5 milliseconds,.in the middle of each 20 millisecond unit interval, and a train of counting relays BB, CC, DD, EE and FF counts the swings of the pendulum relay and causes it to be locked up when the character has been received. A second pendulum relay PA is used to delay the release of the first pendulum relay PB, so that the inspection periods occur in the middle of the 20 milliseconds signal intervals. The description below is based on a 5 millisecond inspection period, the first of which lasts from about 27 to about 32 milliseconds after the receipt of the start signal, that is, in the middle of the first code interval. It Will be evident, however that the circuit can be arranged to operate with an inspection period of any desired length, and timed as required, with respect to the code unit elements.

The details of the operation are as follows:

Idle, or ready to operate condition In the working condition of the circuit it is necessary for the two pendulum relays PA and PB to be locked up and for relay HH to be operated. For this purpose a slow-release relay HHR is provided as before. .As soon as the batteries are switched on, HH and PA operate through contacts HHR-i, and PB operates through its winding 11 and HI-IR2. These contacts, however immediately break when HHR is operated by the closing of contacts HHI, the relay HH locking itself and holding PA through its winding h and contacts HH-2 from the earth obtained from contact RR-M. The relay HHR remains operated during the transmission of each character, as before. After the operation of HHR, PE is held through its winding h, and contacts PA-I, AR-l, and FF-l; contacts PA?. being now open.

Efiect of the start signal On receipt of the start signal, the receiving relay RR changes its armature over to the spacing side RR-S. This operates relay AA which looks itself through its contacts AA5 and the contacts FF-2. Relay AA prepares for subsequent operation relays AR (through AA--l PA2 being open); BB (through AA-2); and

VV (through Ali- 3); and further. it prepares a locking earth for the code storing relays VV to ZZ, by closing its contacts AA4.

The removal of the earth connection from RRM also releases the pendulum relay PA, which starts to swing. Nothing further happens until it opens the contacts PA-l which releases the other pendulum relay PB, which thereupon also starts to swing. The closing of the contacts PA2 which occurs at about the same time, operates relay AR which applies earth to the winding d of PA through contacts AR-I for the purpose of looking it up on the return swing. PA plays nofurther part in the transmission of the character. PB continues to execute a few free vibrations until it becomes locked up on the completion of the operation.

The removal of earth from REV-HM also releases relay HH which opens its contacts HH.2; this is in order to prevent subsequent marking signals from affecting relays HE and, PA. HH also closes the contacts 'HH.3 to prepare a locking circuit for relay FF, and an operating circuit for KK.

It will thus be seen that the start signal releases the timing relays and prepares a number of circuits for later operation.

Operation ,of the timing relays The working of the relays PA and PB and. of the other relays will be understood from the diagram of Fig. 4. The various operations are there indicated with reference to a horizontal time scale divided at intervals of milliseconds. The start element is supposed to be received at zero time; the code elements arrive at 20, 40, 60, 80 and 100, milliseconds, and the stop element-at 120 milliseconds as indicated.

It is assumed that the start element for the next character is received again at 140 milliseconds, which is the earliest possible time, and the corresponding first and second unit elements are also shown at 160 and 180 milliseconds.

As already stated, the first inspection is to take place between 27 /2 and 32 /2 milliseconds, and is made to commence when relay P-B closes its contacts P-B--S, as will be presently explained. The relay PBmust execute tree vibrations at as nearly as possible complete cycles per second in order to time the inspection correctly. 'It is found that relays of the type described in the above mentioned specificationand adjusted to 25 cycles take about 12 milliseconds to operate their contacts after being released :from the locked position. The inspection relays arehighspeed relays haviing an operatetime of the orderof '1 millisecond. To achieve the timing mentioned above the relayPA must introduce'a delay of 14% milliseconds and this willbe attained'if the relay i-s ad.- justed to a frequency of about 20 cycles per second. "It will be understood that in practice the PA relay can be adjusted togive the-exact time required'for the-case quoted above or to function with an inspection period *of any other duration Which may be convenient.

Thus in'Fig. .4, relay PA is-released by -the start signal at zero time, "It opens the contacts'PAl and releases PB at 14 /2 milliseconds. 'PBswings over to thePB- Sside at about 2't /2milliseconds. Meanwhile, of course,: relay RRjhas changed back to the mark ng side .for the first code element (assuming the character 3 as beforeL-but this h s no immediat fiect. .Thechanging over-of the armature ,of relayPB ha,s;rernoved the "earth from the inspecting :relay 5 1B and applied it --.t.o

10 the other inspecting relay HA. These two relays should be very quick to operate, but should be given a releasing time of say, 5 or 6 milliseconds by means of the rectifier and condenser arrange-. ment shown, for example. ll hus HB does not release until about 132 /2 milliseconds, while HA is operated at 27 /2 milliseconds, so that both relays are operated tQgether for the required eriod of about 5 milliseconds in the middle of the code interyal. Thus the circuit leading from the spec-.- ing contact RR-S to the contacts of the count:- ing relays isclosed for this period only, through the relay contacts JHATTI and HB-.-|. This can be seen from Fig. 4, where the horizontal lines marked HA and denote the periods during which these relays have their contacts closed: the 5 millisecond overlap is clearly shown with reference to the operations of PB. It will be clea that the same process occurs in the middle of each of the code interyals. At approximately 4.0-

milliseconds, the relay ;PA Swings back and locks up, as shown by the graph labelled PA. PB goes on swin in until locked up at about 127% milliseconds, after the operation of relay FF as will be explained later on.

ti n of the c un ing nd ode t n r ax/.8

The relay :has'been prepared for operation by the closing of contacts AA--3, and if the first code unit element is a space, it will be operated and locked through its contacts VV-tdurihg the first inspection period, but not otherwise. Relay B5B, prepared by contacts AA-.-2, is energised on the swinger PB-S at 271 /2 milliseconds and operates at about 40 milliseconds, and cuts off W and ipreparesCG for operation at'about 17 /2 milliseconds .on the next swing of the relay PB. Relay *BB remains operated for about 50 milliseconds .until about so milliseconds, by reason of the resistance q shunting its winding. Relay .BiB also prepares by closing its contacts B1371, which will operate in the second code interval for the character The same series of operations then follows. Relays CC, DD and EEcperate one after the othenallowing XX, and ZZ to operate if the corresponding code element is .aspace.

When relay E .has operated, by closing its contacts'Efl-az :it :prepares relays FF and KK to be energised :by the pendulum :relay on-its swing at 101 /2 milliseconds. These relays operate at about 1201milliseconds. Relay K-Kre-operates relay by'clcsingzitsicontacts KK-l, which then locks .on receipt .of the stop element. Relay FF releases .and locks up through the contacts FEFe h lding KK r ised at the same time. When drl H has operated at about 132-milliseconds, FF and KK are disconnected by the openingoi the .contacts HI-1T3 and irelease about 12 milliseconds :later (since they are unshunted).

The relay by closing its contacts Kl to K.-;5l connects .earth :to :the terminals 1-to'5 according :to the .setting of the code storing relays V)! to Z2, *Flihisearth is obtained through contacts FAA- 4, and relayiprovides an alternatiyeear-th through contacts KK-B because relay AA ;is released ,bBfOFB :the operation is complete. When relay K is fin-allyreleased at about 144 milliseconds tzpFigA) it disconnects allthe code storing relays which have been operated and these :relays all releaseat about 158 milliseconds. All theioperations which have been described are diagrammaticallyzshown in-Fig. 4.

-ilifzhile the operate ,and -re1ease times of these relays are not of .qcritical importance, it is necessary that these times should not be so long that the code relays fail to release before about 160 milliseconds. It is possible for the second character to be transmitted so closely following the 'first that the interval between the stop and the start elements is reduced to 20 milliseconds. The first inspection interval for the second character can thus occur from 167 to 172 /2 milliseconds shown at is in Fi 4, and it is therefore clearly necessary that the code storing relays should be released before this interval.

The swing of the pendulum relay PB at 107 milliseconds is the last effective swing, and it must be locked up on its return at 127 milliseconds. The operation of relay FF provides the necessary locking circuit by closing its contacts FF-l. In the meanwhile, the release of AA has released AR by opening its contacts AA-l. This takes the locking ground off relay PA (now held through winding h), and prepares the holding circuit for PB through AR-l and PA-l. When relay FF is finally released after the operation of KK, the earth is transferred from the winding (2 to the winding h of relay PB, and the circuit is restored to the idle condition.

It will be noted that the contacts AA-fi associated with the winding of relay EE disconnect the shunting resistance q when AA is released. This is to ensure the release of EE.

The timing of the release of the inspecting relays HA and HE is carried out by shunting the windings with condensers CA and CB respectively having current limiting resistances of low value connected in series, and by providing the series rectifiers JBI and JA2. Each relay is energised through the associated rectifier and should operate very quickl as already explained, and the condenser is at the same time charged. When the circuit is broken by the pendulum relay PB, the condenser discharges through the relay holding it operated for the desired time, the other path being blocked by the rectifier. Two other rectifiers JAZ and JB2 are provided to block the undesired alternative paths through the confacts of the counting relays by which the inspecting relays could be operated.

The earth for operating the code storing relays VV to ZZ is only applied for the 5 millisecond inspection period, and in order to ensure their proper operation, their windings are shunted by condensers CV, CW, CX, CY and CZ in series with current limiting resistances. Each condenser is charged up at the same time as the relay is energised, and. when the circuit is bro-ken at HA-I or HB-l, the condenser discharges through the winding of the relay and ensures its complete operation, and it then locks itself as already explained.

It will be understood that the final eifect of receiving a character is that relay KK momentarily connects to earth any of the terminals I to 5 for which the corresponding code signal element is a space. It is assumed that these terminals will be connected to some storage or indicating device of any desired type: for example each terminal could be connected to a self-locking relay which operates a corresponding lamp; or the particular combination of relays which are operated would operate a lamp corresponding to the character transmitted. Additional contacts on the relay KK with corresponding terminals could be provided for performing other operations, such as for stepping up a selector switch for setting up several characters in succession. These arrangements are not anypart 12 of the invention and will be supplied as required by those skilled in the art.

By combining the circuits of Figs. 1 and 3 a start-stop regenerative repeater may be obtained. One way of doing this would be to provide the code storing relays VV to ZZ of Fig. 3 with the same contact combinations as those of Fig. 1 and to connect them in place of those relays. The code setting relays CA to CZ and DS would be omitted, and a starting contact operated for example by relay BB, Fig. 3, would replace DS-I or 02-! in Fig. 1. Distorted signals received by the relay RR in Fig. 3 would be inspected by the code storing relays VV to ZZ which would prepare the relay SR in Fig. 1 for operation in the manner already described, and accurate signals would be sent out again, timed by the pendulum relay P in Fig. 1. Unnecessary duplication of relays could, of course, be removed. Other simpler arrangements of the combined circuit are possible and will be easily prepared by those skilled in the art in accordance with the principles which have been explained.

For claims to the regenerative repeater just described, as well as claims to the receiver, per se, reference is to be had to our divisional application No. 660,100, filed April 6, 1946.

Although the invention has been described for clearness in terms of particular embodiments, it is not intended to be limited thereto, nor to the numerical values which have been quoted as examples.

What is claimed is:

1. A telegraph system for start-stop code signals comprising a relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, a coding apparatus for producing sequential code elements, electrical means for causing said armature to time the operation of said coding apparatus, and means for simultaneously setting said coding apparatus and operating said means for releasing said holding means.

2. A telegraph system in accordance with claim 1, in which the relay is a pendulum relay.

3. A telegraph system in accordance with claim 1, in which the relay has a vibrating armature.

4. A telegraph system in accordance with claim 1, in which the code elements of the coding apparatus include a start element and a stop element.

5. A telegraph system in accordance with claim 1, in which the coding apparatus comprises means to store information relating to a combination of code elements corresponding to any character to be transmitted, means to transmit the information so stored, and means to release said storing means after the transmission of said information.

6. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of counting relays operated in sequence by alternate oscillations of the oscillating relay.

7. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of counting relays operated in sequence by alternate oscillations of the oscillating relay and the operation of each counting relay except the last prepares a circuit for the operation of the- 13 n'eir't relay in the series and in the e'pr'fation of each counting relay except the first 'd-is= connects the winding of the preceding relay in the series.

8. A telegraph system ihaccordance with claim 1, in which the coding apparatus comprises a train of counting relays operated in sequence by alternate oscillations of the oscillating relay and the operation of each counting relay except the last prepares a circuit for the operation of the next relay in the series, and in which the operation of each counting relay except the first disconnects the winding of the preceding relay in the series, and in which at least one of the counting relays is provided with means for delaying the release thereof after disconnection by the preceding relay until after the heat relay has operated.

9. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of counting relays operated in sequence by alternate oscillations of the 'osc'i-ll-ati ng relay and the operation of each counting relay except the last prepares a circuit for the operation 'of the next relay in series, and in which the operation of each counting relay except the first disconnects the winding of the preceding relay in the series, at least one ofthe counting relays being provided with a resistance connected in shunt therewith for delaying the release after discon nect'ion by the preceding ien until after the next relay has operated.

10. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of counting relays operated in sequence by alternate oscillations of the oscillating relay and in which the operation of the last counting relay by the oscillating relay prepares a circuit for locking the armature of the oscillating relay on the next following swing.

11. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of code storing relays equal in number to the number of units in the code for storing information relating to a combination of code elements corresponding to any character to be transmitted, means to transmit the information so stored, and means to release said storing relays after the transmission of said information.

12. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of code storing relays equal in number to the number of units in the code for storing information relating to a combination of code elements corresponding to any character to be transmitted, means for locking said relays after operation, means to transmit the information so stored, and means to release said storing relays after the transmission of said information.

13. A telegraph system in accordance with claim 1, in which the coding apparatus comprises a train of code storing relays equal in number to the number of units in the code for storing information relating to a combination of code elements corresponding to any character to be transmitted, means to operate a code storing relay only when the corresponding code unit element is a space, means to transmit the information so stored, and means to release said storing relays after the transmission of said information.

14. A telegraph code sender for start-stop code signals comprising a relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, a plurality of code stor ing relays, electrical means controlled by said oscillating relay for selectively operating said code storing relays in accordance with the code corre spending to any character to be transmitted, and means for simultaneously operating said means for releasing said holding means when a code is introduced into said sender.

15. A telegraph code sender in accordance with claim 14, in which the means for operating the code storing relays comprises one or more code setting relays corresponding toseach character, the operation of which relays causes operation of the appropriate cod-e storing relays.

16. A telegraph code sender in accordance with claim 14, in which one code setting relay is prervided for every pair of characterswhich differ only in the last unit element, two other code set ting relays being provided, the first of which is common to all characters having a final marking element and the second of which is common tothe remaining characters. a

7 17. A telegraph code sender in accordance with claim 14, in which one code setting relay is provided for every pair of characters which differ only in the last unit element, two other code setting relays being provided, the first of which is common to all characters having a final marking element and the second of which is common to the remaining characters, and in which is providedmeans to cause the operation of the second common relay to operate the last code storing relay, and means to cause the operation of either of the common relays to cause the release of said oscillating relay.

18. A telegraph code sender in accordance with claim 14, in which the operation of the last counting relay prepares a circuit for locking the armature of the oscillating relay on the next following swing, and in which the last counting relay is provided with break contacts for releasing the code storing relays when said last counting relay is operated by the penultimate swing of said, 0scillating relay.

19. A telegraph code sender in accordance with claim 14, in which the means for operating said code storage relays comprises one or more character keys with associated relays, adapted on operation to set the code storing relays in accordance with the code for the corresponding character, and at the same time to release said oscillating relay.

20. A telegraph code sender in accordance with claim 14, comprising a polar sending relay for transmitting the code signals to the outgoing line, the said polar relay having a marking and spacing winding, one of which is adapted to be energized in series with a counting relay on each swing of the oscillating relay.

21. A telegraph code sender in accordance with claim 14, comprising a polar sending relay for transmitting the code signals to the outgoing line, the said polar relay having a marking and spacing winding, one of which is adapted to be energized in series with a counting relay on each swing of the armature of said oscillating relay, and in which each coding storing relay is provided with contacts adapted to prepare the spacing winding or the marking winding of said polar relay for energization on the corresponding swing of the armature of said oscillating relay, accord- 15' ing as said storing relay is or is not operated respectively.

22. A telegraph code sender in accordance with claim 14, provided with testing means under the control of a test key for causing the sender periodically to repeat the transmission of any given character.

23. A telegraph code sender in accordance with claim 14, provided with testing means under the control of a test key for causing the sender periodically to repeat the transmission of any given character, and means for giving the oscillation relay an impulse once during each cycle of the test operation for the purpose of maintaining said relay in oscillation.

24. A telegraph code sender in accordance with claim 14, in which a train of counting relays is arranged to operate the code storing relays and in which testing means is provided under the control of a test key for causing the sender periodlcally to repeat the transmission of any given character, and in which said testing means comprises an extra counting relay adapted to be adapted to be added to the counting train on operation of the test key in such a manner that it is prepared for operation by the last counting relay and when operated by the oscillating relay it disconnects the said last counting relay and prepares the first counting relay for operation on the next swing of the oscillating relay.

25. A telegraph code sender in accordance with claim 14, provided with testing means under the control of a test key for causing the sender periodically to repeat the transmission of any given character and with means associated with the test key for preventin the release of the code storing relays at the end of each test cycle.

26. A telegraph code sender in accordance with claim 14, in which there are five code storing relays and in addition seven counting relays, the apparatus being arranged so that the armature of the oscillating relay will make eight single swings during the transmission of each character.

GEORGE CLIFFORD HARTLEY. WILLIAM JOHN REYNOLDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,374,152 Krum Apr. 5, 1921 1,199,011 Krum Sept. 19, 1916 1,305,225 Krum May 27, 1919 1,196,528 Dixon Aug. 26, 1916 1,232,045 Krum July 3, 1917 1,730,614 Knoop Oct. 8, 1929 2,128,242 Graham Aug. 30, 1938 1,197,542 Potts Sept, 5, 1916 

